Hospitalizations for asthma have been dramatically cut by a program that helps families reduce the conditions that trigger attacks, saving $1.46 in hospital care for every $1 spent on prevention, according to a Children’s Hospital Boston study being released today.

The actual article was e-published by Pediatrics today. The link to the article is here. Harvard Link

The truth, as always, is murkier than the headline.

First of all – this study is laudable for many reasons. It aimed to lower the asthma morbidity in underprivileged communities – which is where asthma has the most devastating impact. Asthma hospitalization rates are five times higher among Blacks and Hispanics compared to whites – and the study group was largely Black and Hispanic. The researchers sifted through the literature about what works, and developed a multidisciplinary intervention based on this literature. They measured carefully. They counted only “hard” savings like decreased hospitalizations and ED visits, and did not attribute monetary value to

Researchers made notable efforts to be culturally sensitive, and offered home community health worker and nursing visits, supplies to help decrease allergens, and even special vacuum cleaners to decrease airborne particulate matter. When necessary, the program did extermination to help prevent exposure to allergens that could trigger asthma attacks.

Now, the concerns.

This is a study with 283 patients, who were handpicked by researchers because they appeared to be at highest risk for recurrent emergency department visit or hospitalization based on their recent history. The study was offered to 562 families; so the take-up rate was about 50%. The cost savings are comparing these study patients with patients from different zip codes – who were not subject to the same selection process.

Note that the study was designed in 2003 and carried out from 2005-2008. This gives you the sense of how complicated these studies are to complete.

Here are two reasons why this study likely overstates the benefit from this intervention

Regression to the mean. Those asthmatics who are chosen because they appear very ill today will as a group always have far fewer hospitalizations and ED visits going forward than they had in the recent past. Here’s a link to a 2004 study where the control group (no intervention) had more than a 30% decrease in cost. Here’s a link to my letter to the editor, where I pointed out that even this understated the true amount of regression to the mean.

Selection bias. The families that were willing to participate and were able to persist in the intervention likely had more means than those who refused, were unable to be reached, or dropped out during the course of the trial. The stated control group did not have such selection.

To the Globe’s credit, the last two paragraphs quote a researcher who points out that this was not a randomized controlled trial.

It’s heartening that it appears that there was some decrease in asthma morbidity that coincided with this intervention. I would be very cautious about the cost-saving claims from this article.

Two major public health interventions to lower asthma morbidity – decreasing air pollution and decreasing parental and teenage smoking rates, are not mentioned in the article. We tend to overemphasize interventions in the medical model while we underinvest in effective public health interventions.